Reading method of reading information from a recording medium and medium used therefor

Abstract

An information recording medium and a reading method thereof for realizing high density recording and recording/reading a direction of magnetization at minute bit length and bit width, which comprises a substrate having a first magnetic layer which is capable of thermo-magnetically recording and a second magnetic layer which is capable of being exchange coupled with the first magnetic layer formed thereon in this order, is performed by detecting a direction of magnetization transferred onto the second magnetic layer from variations in magnetic flux while emitting a light beam thereon.

What is claimed is: 
     
       1. An information recording medium comprising: a substrate;   a recording layer in which information is thermo-magnetically recorded; and   a reading layer having a temperature characteristic which allows the transfer of the direction of magnetization on the recording layer thereto by exchange coupling force; wherein the recording layer is located nearer to the substrate than the reading layer.     
     
     
       2. An information recording medium reading a recording bit which is smaller in size than a spot diameter of an emitted light beam, the information recording medium comprising: a substrate;   a first magnetic layer for thermo-magnetically recording;   a second magnetic layer having a temperature characteristic by which a direction of magnetization recorded on the first magnetic layer is transferred thereon by magnetic coupling force; and   a controlling layer provided between the first magnetic layer and the second magnetic layer for controlling the magnetic coupling force, wherein the first magnetic layer is located nearer to the substrate than the second magnetic layer.     
     
     
       3. The information recording medium according to claim 1, wherein the recording layer includes Tb, Fe, and Co. 
     
     
       4. The information recording medium according to claim 1, wherein the recording layer includes Dy, Fe, and Co. 
     
     
       5. The information recording medium according to claim 1, wherein the reading layer includes Gd, Fe, and Co. 
     
     
       6. The information recording medium according to claim 1, wherein the reading layer includes a composite film comprised of Pt and Co. 
     
     
       7. The information recording medium according to claim 2, wherein the first magnetic layer includes Tb, Fe, and Co. 
     
     
       8. The information recording medium according to claim 2, wherein the first magnetic layer includes Dy, Fe, and Co. 
     
     
       9. The information recording medium according to claim 2, wherein the second magnetic layer includes Gd, Fe, and Co. 
     
     
       10. The information recording medium according to claim 2, wherein the second magnetic layer includes a composite film comprised of Pt and Co. 
     
     
       11. The information recording medium according to claim 2, wherein the controlling layer includes Gd and Fe. 
     
     
       12. The information recording medium according to claim 2, wherein the controlling layer is of a non-magnetic material. 
     
     
       13. A reading method of an information recording medium comprising at least a first thermo-magnetically recorded magnetic layer and a second magnetic layer provided on a substrate, the reading method comprising the steps of: emitting a light beam from a side of the substrate so that a direction of magnetization recorded on the first magnetic layer is transferred onto the second magnetic layer;   detecting variations in magnetic flux on a region of the second magnetic layer corresponding to an irradiated region of the light beam by means of a magnetic head which moves relative to the information recording medium; and   reading an information recorded in the information recording medium based on the detected results.   
     
     
       14. The reading method of the information recording medium according to claim 13, wherein the first magnetic layer for thermo-magnetically recording is located nearer to the substrate than the second magnetic layer having a temperature characteristic by which a direction of magnetization recorded on the first magnetic layer is transferred thereon by magnetic coupling force; and   the magnetic head is arranged as to be opposing to a side opposite to the substrate.   
     
     
       15. The reading method of the information recording medium according to claim 13, wherein the information recording medium reads a recording bit smaller in size than a spot diameter of an emitted light beam by further providing a controlling layer between the first and second magnetic layers for controlling the magnetic coupling force;   the first magnetic layer for thermo-magnetically recording is located nearer to the substrate than the second magnetic layer having a temperature characteristic by which a direction of magnetization recorded on the first magnetic layer is transferred thereon by magnetic coupling force; and   the magnetic head is arranged as to be opposing to a side opposite to the substrate.   
     
     
       16. A method of reading an information recording medium having at least a first magnetic layer and a second magnetic layer provided on a substrate, the reading method comprising the steps of: detecting variations in magnetic flux on a region of the second magnetic layer on which a direction of magnetization recorded on the first magnetic layer is transferred, by means of a magnetic head which opposes a side opposite to the substrate and moves relative to the information recording medium; and   reading information recorded in the information recording medium based on the detected results, wherein the first magnetic layer for thermo-magnetic recording is located nearer to the substrate than the second magnetic layer, a direction of magnetization recorded on the first magnetic layer being transferred to the second magnetic layer by magnetic coupling force.     
     
     
       17. An information recording medium comprising: a substrate;   a first magnetic layer for thermo-magnetically recording;   a second magnetic layer having a temperature characteristic by which a direction of magnetization recorded on the first magnetic layer is transferred thereon by magnetic coupling force; and   a controlling layer provided between the first magnetic layer and the second magnetic layer for controlling the magnetic coupling force, wherein the first magnetic layer is located nearer to the substrate than the second magnetic layer.